Stepper motors are often used to drive mechanical loads through a belt and pulley transmission system. Such an arrangement is used for instance for moving a typewriter/printer print carrier from one print position to the next. Proper printing may only be achieved through precise carrier positioning. This is particularly true with open loop systems in which no feedback position control is provided, which means that any incorrect carrier positioning would result in subsequently repeated improperly positioned printings.
Generally, the stepper motor is controlled through a processor using prestored escapement algorithms specifically developed for a designed typewriter/printer. These algorithms are based on a number of parameters among which load related parameters, such as stepper motor load natural frequency are most critical. The load natural frequency is predetermined for a designed machine but varies while the machine is being operated mainly due to belt tension variations, and in production of the machine due to carrier mass variations and belt spring rate variations. Therefore, adjustments are always required to bring that natural frequency back to the original value for which the escapement algorithms where determined when the machine is in use. A commonly used method for performing load natural frequency adjustment or tuning involves using weighting gauges. The maintenance engineer adjusts the belt tension for a given belt dip to be provided by the gauge set at a predetermined belt position. In addition to the burden of having the engineer carry around an additional tool and to any problems involved in accessing the specific belt position, the mentioned method lacks precision for not taking into consideration parameters other than belt tension measurement per se.